Autism spectrum disorder (ASD) is a developmental disorder that impairs social interaction and communication, causes one afflicted to have unstable feelings and emotions, and impairs cognitive development in many cases. ASD is also called a pervasive developmental disorder, because it is not a term that designates a kind of developmental disorder, but a term that designates, in a broad sense, diseases sharing various characteristic symptoms. In recent years, the prevalence of ASD in each country has increased, and thus the social and economical costs associated with ASD have increased and the quality of life of the patient's family has decreased. For this reason, studies on the establishment of the cause of ASD and the development of agents for treating ASD have been increasingly required. With respect to the cause of ASD, various risk factors have been studied, and genetic tendency, viral infection, abnormal metabolism and other environmental factors including rearing methods, have typically been known as risk factors and causes. However, specific evidence of the cause of development of ASD is still insufficient.
In recent years, studies on the genetic factors of ASD in animal models have been actively conducted, and various genes believed to have a close relation with ASD have been found through genetic studies on ASD patients. Because ASD shows a high heritability compared to other mental disorders, such studies on the genetic factors of ASD are important to widen the understanding of the biological causes of ASD and develop effective therapeutic agents against ASD. Shank2 protein is a scaffolding protein enriched at excitatory neuronal synapses and is known to interact with other various proteins in neuronal dendrites and play an important role in synapse signaling. As it has been reported that mutations in the Shank2 gene were found in ASD patients, it has been believed that the Shank2 gene is highly likely to be associated with ASD.
Accordingly, the present inventors have made extensive efforts to clarify the cause of ASD, and as a result, have found that the clinical features of ASD appear in a genetically engineered mouse carrying a deletion of the Shank2 gene.